Generally, a cutting insert is fastened to a cutting tool mounted on a machine tool and is used for cutting a workpiece made of iron, non-ferrous metal, non-metal material, and so on.
Such cutting insert typically has a principal surface, a fastening surface, and a plurality of side surfaces connecting the principal surface and the fastening surface. A cutting edge is provided between the side surface and the principal surface.
FIG. 1 is a cross-sectional view illustrating a related cutting insert mounted on a fastening surface of a cutting tool, taken elsewhere from a clamping screw and a bore, FIG. 2 is a bottom perspective view of the cutting insert of FIG. 1, FIG. 3 is a top view of the lower wall of the cutting tool of FIG. 1, and FIG. 4 is a side view of the cutting tool of FIG. 1.
As shown in FIGS. 1 to 3, an example of the related technology can be found in the cutting insert 14 disclosed in Korean Patent No. 10-0830323, which is provided with two parallel grooves 74 that are formed side by side on a bottom surface (i.e., fastening surface) 60 of the cutting insert 14 and that are respectively engaged with the front protrusion 40 and the rear protrusion 42 protruding from the lower wall 26 of a cutting tool 12. Specifically, each of these two grooves 74 includes a distal sidewall 76 perpendicular to the bottom surface 60, a proximal sidewall 78 that is inclined with respect to the bottom surface 60 and adjacent to the bore 36 of the cutting tool 12 closer than the distal sidewall 76, and an upper surface 80 that connects the proximal sidewall 78 to the distal sidewall 76 and is parallel with respect to the bottom surface 60, as shown in FIGS. 1 and 2.
Accordingly, as shown in FIG. 1, the protrusions 40, 42 of the insert receiving pocket 16 are engaged with the corresponding grooves 74 in the bottom surface 60 of the cutting insert. However, due to the tolerances, only one side of the protrusions 40, 42 is in contact with the cutting insert 14 during cutting process. That is, while the distal cutting edge of the cutting insert 14 is pressing on and cutting the workpiece in the direction of the rotational axis (Ain FIG. 4) of the cutting tool 12, the front surface 46 of the front protrusion 40 is brought into contact with the front distal sidewall 76 of the front groove 74 to support the force exerted on the cutting insert 14.
However, since the related cutting insert 14 described above has a distal sidewall 76 perpendicular to the bottom surface 60 which is in contact with the front surface 46 of the front protrusion 40 perpendicular to the lower wall (i.e., seat surface) 26 of the cutting tool 12 (46), considering that the lower wall 26 of the cutting tool is inclined by “α” with respect to the rotational axis A as shown in FIG. 4, when a force is exerted to the cutting insert 14 in the direction of the rotational axis A, there is a problem that the cutting insert 14 is lifted up from the lower wall 26 of the cutting tool as the distal sidewall 76 is moved along the front surface 46 of the front protrusion 40.
In another example of the related technology that can be found in the cutting tool 12 disclosed in Korean Patent No. 10-0830323, the cutting tool 12 includes a front protrusion 40 and a rear protrusion 42 protruding from the lower wall 26, as shown in FIG.3. Specifically, as shown in FIG. 3, each of these two protrusions 40, 42 has a length spanning from the outside of the lower wall 26 to the center of the bore 36.
That is, while the distal cutting edge of the cutting insert 14 is pressing on and cutting the workpiece in the direction of the rotational axis (A in FIG. 4) of the cutting tool 12, the front surface 46 of the front protrusion 40 is in contact with the front distal sidewall 76 of the front groove 74 to support the force exerted on the cutting insert 14.
However, in the related cutting tool 12, since each of the protrusions 40, 42 is extended only up to the center of the bore, while the cutting tool 12 is being transferred in a direction perpendicular to its rotational axis (A of FIG. 4), there is a problem that the cutting insert 14 is rotated about the bore 36 by the radial load generated from the side cutting edge of the cutting insert 14 pressing on the workpiece.